As illustrated in FIG. 46, a steering apparatus for an automobile is constructed so that rotation of a steering wheel 1 is transmitted to an input shaft 3 of a steering unit 2, and as the input shaft 3 rotates, a pair of left and right tie rods 4 are pushed or pulled, applying a steering angle to the front wheels. The steering wheel 1 is supported by and fastened to the rear end section of a steering shaft 5, and with this steering shaft inserted in the axial direction through a cylindrical shape steering column 6, the steering shaft 5 is supported by the steering column 6 so as to be able to rotate freely. Moreover, the front end section of the steering shaft 5 is connected to the rear end section of an intermediate shaft 8 by way of a universal joint 7, and the front end section of this intermediate shaft 8 is connected to the input shaft 3 by way of a separate universal joint 9.
Conventionally, in this kind of steering apparatus, a tilt mechanism for adjusting the up/down position of the steering wheel 1 and/or or a telescopic mechanism for adjusting the forward/backward position of the steering wheel 1 according to the size and driving posture of the driver have been widely known. In order to construct the tilt mechanism, the steering column 6 is supported by the vehicle body 10 so as to be able to pivot around a pivot shaft 11 that is arranged in the width direction. In order to construct the telescopic mechanism that can displace in the forward/backward direction, the steering column 6 is constructed by combining an outer column 13 and an inner column 14 so as to be able to expand and contract freely in a telescopic manner, and the steering shaft 5 is constructed by combining an outer shaft (outer tube) 15 and an inner shaft 16 with a spline fit or the like such that torque can be freely transmitted, and so as to be able to expand and contract freely. A displacement bracket that is fastened to the portion of the steering column 6 near the rear end section is supported by a support bracket 12 that is supported by the vehicle body 10 such that the displacement bracket can displace in the up/down direction and forward/backward direction. Here, the width direction means the width direction of the vehicle, and corresponds to the left/right direction. Also, the forward/backward direction is the forward/backward direction of the vehicle. In the example illustrated in the figure, in order to reduce the force required for operating the steering wheel 1, an electric power steering apparatus, having an electric motor 17 as the source of assist power, is also assembled in the steering apparatus.
In a steering apparatus that comprises a tilt mechanism and a telescopic mechanism, construction is necessary wherein the position of the steering wheel 1 can be adjusted, and can be fastened at the adjusted position. FIG. 47 and FIG. 48 illustrate construction that is disclosed in JP2001-322552(A) wherein by rotating a rod shaped member 19 by an adjustment lever 18, the dimension in the width direction of a cam apparatus 20 is expanded or contracted, and at the same time a cam member 21 pivots and displaces. In this construction, due to the expansion or contraction of the cam apparatus 20, it is possible for a displacement bracket 22 that is fastened to the outer column 13a to engage with or disengage from a fastening bracket 12a. Moreover, it is possible to switch whether or not to allow relative movement of the inner column 14a with respect to the outer column 13 according to the pivotal displacement of the cam member 21.
The outer column 13a and inner column 14a of the steering column 6a of this kind of steering apparatus fit together such that the inner circumferential surface on the portion near the front end of the outer column 13a and the outer surface of the portion near the rear end of the inner column 14a are capable of relative displacement in the axial direction. Moreover, when the manufacturing the outer column 13a, first the main outer column is formed by aluminum die casting. After that, the inner circumferential surface of the main outer column is machined and finished. On the other hand, the displacement bracket 22 is formed separate from the outer column 13a, and integrally joined and fastened to the part of the outer column 13a by welding.
In the case of this kind of steering apparatus, it is necessary to finish the inner diameter of the outer column 13a with good precision, however, there is a problem in that the machining work is troublesome and costly. Furthermore, the inner circumferential surface of the outer column 13a and the outer circumferential surface of the inner column 14 fit all the way around, so in the case that the precision of the inner diameter of the outer column 13a is not sufficient, there is a problem in that the columns may become off centered, and the inner column 14a cannot be stably held on the inner-diameter side of the outer column 13a. 
FIG. 49 illustrates construction that is disclosed in JP2008-302751(A), wherein raised sections 23 that protrude inward in the radial direction from the inner circumferential surface of the outer column 13b are formed at a plurality of locations in the circumferential direction of the inner circumferential surface of the outer column 13b that overlap the outer circumferential surface of the inner column 14a, and the tip end section (inside end sections in the radial direction) of these raised sections 23 come in contact with the outer circumferential surface of the inner column 14a. In this construction, of the inner circumferential surface of the outer column 13b, machining and finishing such as broaching only needs to be performed for the tip end section of the raised sections 23, so it is possible to reduce the processing cost.
When manufacturing the outer column 13b, first the main outer column is formed by aluminum die casting, hydroforming or the like. After that, forging and broaching is performed on a plurality of locations (eleven locations in the figure) in the circumferential direction of portions of the inner circumferential surface of the main outer column that overlap with the outer circumferential surface of the inner column 14a to form the raised sections 23 that protrude inward in the radial direction from the inner circumferential surface of the outer column 13b. However, in this case as well, the method for forming the outer column 13b and the method for form the raised sections 23 differ, so processing requires time and labor, so an increase in cost is unavoidable.
In order to stably support the inner column 14a on the inner-diameter side of the outer column 13b with the column being off center or without backlash or the like occurring, preferably all of the raised sections 23 will come in contact with the outer circumferential surface of the inner column 14a in the same contact state. However, the processing work for achieving the same contact state for a plurality of raised sections 23 is troublesome.
FIG. 50 illustrates construction of a steering column 6c that is disclosed in JP2008-302751(A). The outer column 13c of this steering column 6c is formed into a cylindrical shape by being a plate shaped material and welding together the edges on the end in the circumferential direction (top edges in FIG. 50). Moreover, support tabs 24 are formed in three locations in the circumferential direction of the inner circumferential surface of the outer column 13c such that these support tabs 24 face the outer circumferential surface of the inner column 14a in the assembled state. The support tabs 24 are formed by pressing part of the outer column 13c and bending that part toward the inside in the radial direction from the inner circumferential surface of the outer column 13.
The displacement bracket 22a is provided on part in the axial direction of the outer circumferential surface of the outer column 13c. The displacement bracket 22a is formed by bending a plate shaped raw material that is the same as the material used for forming the outer column 13c so that the edge on one end is continuous with the outer circumferential surface of the outer column 13c, and the edge on the other end is welded to this outer circumferential surface, forming a pair of left and right clamped sections 25.
In the case of the outer column 13c, support tabs 24 are formed at three uniformly spaced locations in the circumferential direction. Therefore, processing for making the contact state between the tip end edges of all of the support tabs 24 and the outer circumferential surface of the inner column 14a the same can be performed easily. However, the support tabs 24 have cantilever like construction, so there is a problem in that it is difficult to maintain rigidity for stably supporting the inner column 14a on the inner-diameter side of the outer column 13c. 
Furthermore, in the telescopic steering apparatuses having these kinds of conventional construction, the longer the dimension in the axial direction of the portion of the outer column 13 and inner column 14 that overlap in the radial direction is, the higher the rigidity in the width direction of the displacement bracket 22 becomes, and it becomes difficult to bend. Therefore, it is necessary to change the operating force applied to the adjustment lever depending on the dimension in the axial direction of the portion of the outer column 13 and inner column 14 that overlap in the radial direction. As a result, there is a possibility that operability of the adjustment lever 18 will become unstable, and that it will not be possible to provide stable support rigidity (tightening force) to the inner column 14.
Moreover, in a typical telescopic steering apparatus, when adjusting the position of the steering wheel 1, the adjustment lever 18 is operated in a specified direction, which decreases the friction force acting between the fastened bracket 12a and the displacement bracket 22. On the other hand, when maintaining the steering wheel 1 at the adjusted position, the adjustment lever 8 is operated in the opposite direction of the specified direction, which increases the friction force between these brackets. In this kind of construction, the amount that the adjustment lever 18 is operated is not large, and in order to increase the force for maintaining the steering wheel 1 in the adjusted position, preferably the number of friction surfaces is increased, increasing the friction surface area. JP2008-100597(A), JP10-35511(A), JP2007-69821(A), JP2011-5896(A) and JP62-19483(Y) disclose construction in which the number of friction surfaces is increased by layering together a plurality of friction members.
FIG. 51 and FIG. 52 illustrate an example of the construction of the telescopic steering apparatus disclosed in JP2011-5896(A). In this apparatus, a long hole 29 in the forward/backward direction that extends such that it is long in the axial direction of the steering column 6d is formed in the displacement bracket 22b for inserting the rod shaped member 19, and is formed such that it passes through the displacement bracket 22 in the left/right direction (width direction). On the other hand, the fastened bracket 12a is formed by joining and fastening together an upper bracket element 26 and a lower bracket 27, which are both formed by bending metal plate. The upper bracket element 26 is supported by the vehicle using known construction so as to be able to break away in the forward direction during a secondary collision. Moreover, the lower bracket element 27 comprises a pair of left and right support plate sections 28 that are separated from each other in the width direction. The distance D between the inside surfaces of these support plate sections 28 coincides with the space W between the outside surfaces of the displacement bracket 22b (width of the displacement bracket 22b) (D≈W). Partial arc shaped long holes 30 in the up/down direction that extend such that they are long in the up/down direction centered around a pivot shaft 11 are formed in positions in the pair of support plate sections 28 that are aligned with each other, and are for inserting the rod shaped member 19 through. A plurality of first friction plates 31 and second friction plates 32 are arranged on portions on the outsides of the support plate sections 28.
First long holes 33 are formed in the first friction plates 31, and second long holes 34 are formed in the second friction plates 32. The end sections of the first friction plates 31 are connected to and supported by outside surfaces on the top end of the support plate sections 28 by first locking screws 35, and the end section of the second friction plates 32 are connected to and supported by the outside surfaces on the front end of the displacement bracket 22b by second locking screws 36, thus preventing the first friction plates 31 from displacing in the lengthwise direction of the first long holes 33, and preventing the second friction plates 32 from displacing in the lengthwise direction of the second long holes 34. These kinds of first friction plates 31 and second friction plates 32 are arranged on the outside surfaces of the support plate sections 28 so that they are alternately layered.
The rod shaped member 19 is inserted through the long hole 29 in the forward/backward direction, the long holes 30 in the up/down direction, the first long holes 33 and the second long holes 34. An outward facing flange section 38 is formed on the base end section (right end section in FIG. 52) of the rod section 37 of the rod shaped member 19. Locking convex sections 39, having an elliptical cross section, that are formed in the portion near the base end section of the rod section 37 engages with one of the long holes 30 in the up/down direction (right hole in FIG. 52) so as to be able to freely displace (move up or down) along the long hole 30 in the up/down direction.
On the other hand, a pressure plate 40 is fitted around the portion in the middle section of the rod section 37 near the tip end, that protrudes from the other support plate section 28 (left support plate section 28 in FIG. 52), the first friction plate 31 and second friction plate 32 that are provided on the outside surface of that support plate section 28, and further a cam apparatus 20 is provided on this portion. This cam apparatus 20 and the rod shaped member 19 form a pressure apparatus. The cam apparatus 20 is such that the dimension T in the axial direction thereof expands or contracts according the operation of the adjustment lever 18, and has known construction. When the adjustment lever 18 is rotated in a specified direction, the dimension T in the axial direction expands, and the space between the surface on one side of the pressure plate 40 and the inside surface of the flange section 38 contracts, and the friction force that acts between opposing surfaces that are engaged by a friction fit increases.
In other words, in this state, on both the left and right sides, the contact pressure between the side surfaces of the displacement bracket 22b and the inside surfaces of the support plate sections 28, the contact pressure between the outside surfaces of the support plate sections 28 and the inside surfaces of the second friction plates 32 that are located on the very inside, the contact pressure between the inside surfaces of the adjacent first friction plates 31 and the outside surfaces of the second friction plates 32, and the contact pressure between the outside surfaces of the first friction plates 31 located on the very outside and the surface of one side of the pressure plate 40 or the inside surface of the flange section 38 increase. In this state, the total friction force that acts between these sections of frictional engagement becomes sufficiently large. As a result, it is possible to sufficiently increase the support strength of the displacement bracket 22b with respect to the fastened bracket 12a. 
On the other hand, when adjusting the position of the steering wheel 1, the adjustment lever 18 is rotated in the opposite direction from the specified direction, causing the dimension T in the axial direction of the cam apparatus 20 to contract, and the space between the surface on one side of the pressure plate 40 and the inside surface of the flange section 38 to expand. In this state, the friction force that acts between these sections of frictional engagement is decreased or lost, and it is becomes possible to adjust the displacement bracket 22b in the up/down direction and forward/backward direction with respect to the fastened bracket 12a. In this state, by rotating the adjustment lever 18 in the specified direction after the position of the steering wheel 1 has been adjusted to a desired position, it becomes possible to stably maintain the position of the steering wheel 1 at the desired position.
However, in the case of this kind of conventional construction, there is a problem in that the construction for assembling the first friction plates 31 and the second friction plates 32 is complicated, and thus the manufacturing cost increases. Moreover, when the steering wheel 1 is moved to the very front adjustable position or to the very back adjustable position, there is a possibility that the outer circumferential surface of the rod section 37 of the rod shaped member 19 and the inner surface of the long hole 29 in the forward/backward direction in the displacement bracket 22b, which are both made of metal, will collide with much energy. When these surfaces energetically collide, there is a possibility that the driver operating the steering wheel 1 will feel a strange or uncomfortable feeling. In response to this, JP10-512825(A) (WO96/15931) discloses construction where an impact absorbing sleeve is provided that surrounds the long hole in the forward/backward direction of the displacement bracket. However, construction that combines the construction of providing this impact absorbing sleeve and the construction illustrated in FIG. 51 and FIG. 52 that improves the holding force for maintaining the position of the steering wheel 1 by using a plurality of friction plates is not suggested. These kinds of construction can be independently assembled in a telescopic steering apparatus, however, the assembly work is troublesome and increased costs are unavoidable.
As technology related to the construction of a steering column is method for manufacturing a steering column as disclosed in JP2006-255785 wherein hydroforming is used to form a bulging section in the middle section in the axial direction of a hollow cylindrical shaped raw material, after which this bulging section is formed into a column bracket by forming a through hole through the side wall section of the bulging section.